Although there are more than 80 million pet dogs in the United States, surprisingly few of us have much to do with their reproduction. If you grew up on a farm or you raise champion show dogs then you probably know the intricacies of canine intercourse, but most of us spay or neuter our pets and do our best to discourage humping. The term “doggy style” adds further confusion to the act by implying that human rear-entry sex is the same as canine rear-entry sex.

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Thank the gods it is not.

Here’s how dog sex goes down. When the male attempts to mount the female, his penis is flaccid. In humans, this would constitute a non-starter, but canines are aided by a tiny bone called a baculum. (Read more about baculi and the weird things people do with them in this piece about hibernation from last year.)

Most of us have seen a dog hump. The legs of dinner party guests you were hoping to impress usually take the brunt of such advances, and the resulting motion is not unlike what humans do while having sex. However, the two performances are surprisingly different.

Humans hump to create friction. Friction stimulates the genitals and causes the male to ejaculate. However, when a male dog humps, he’s mostly just trying to get his reproductive organ in the right spot. (Outside of reproduction, both male and female dogs hump. Canine researcher Julie Hecht writes about some of the possible things humping might communicate, including excitement, dominance, and friendship.)

Once the penis is safely inside, true doggy style takes another turn away from the position that shares a name with Snoop Dogg’s seminal album. Blood rushes into the base of the penis, called the bulbus glandis, causing the organ to swell in size. At the same time, the female’s vagina contracts against the penis, creating what’s known as a “copulatory tie,” “coital tie,” or best of all, “dog knot.” The male and female are now physically, literally locked into one another. According to Miller’s Anatomy of the Dog, the main payload of sperm is delivered within 80 seconds of entry, but the dogs have only just begun.

Dogs doing it for the first time can get a little freaked out, as do first-time dog breeders.

As a way of sealing the deal, the male dog will now swing a leg up over the female’s back and stand directly behind her. To clarify, the dogs are still connected, via penis locked into vagina, but they will now stand butt-to-butt until the erection subsides—which usually lasts around 25 minutes but can exceed an hour. More semen is ejaculated during this phase, which is thought to help push the first responders into the uterus and possibly initiate contractions of the uterine tubes.

Apparently, dogs doing it for the first time can get a little freaked out about the prolonged attachment, as do first-time dog breeders. If you should ever find yourself in this situation, TheEncyclopedia of Dog Breeds suggests you prevent the female dog from trying to rip free from the male, because doing so can cause serious injury to the penis. Breeding websites recommend you get down on the floor and comfort the female. Oh, and never ice the dogs’ genitals in an attempt to separate them.

Preposterous as it sounds, coyotes, foxes, and wolves do it this way, too. There’s not much information out there about the evolutionary purpose of the dog knot, though the most obvious theory is that it keeps the couple together long enough for insemination to take place. In addition, the knot prevents other males from immediately mating with the female and displacing the first male’s sperm—as you can see in this video of a third wolf desperately trying to get in on the action and making it weird for everyone involved.

And now perhaps a word of caution. There’s no shortage of canine sex videos on the Internet. In fact, people seem rather fond of uploading movies of their dogs in the awkward position, complete with bizarre mood music. But watching these videos will make YouTube think you want to watch more animal sex videos—lions, tortoises, turkeys—and before you know it, your Internet history starts to look really, really embarrassing.

Jason Bittel serves up science for picky eaters on his website, BittelMeThis.com. He lives in Pittsburgh. Follow him on Twitter.

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